$canvasWidth:300px;
$canvasWidth:300px;
*{
  box-size:border-box;
}
h1{
  text-align:center;
}
.actions{
  text-align:center;
  margin:20px;
}

.seno{
  float:left;
  padding: 20px;
  text-align:center;
}
#canvas,#canvas2,#canvas3{
  border:1px solid #333;
  position:relative;
  float:left;
  width:$canvasWidth;
  height:$canvasWidth;
  margin:0 auto;
}
.cube{
  position:absolute;
  border:1px solid #333;
  &.active{
    background:#333;
  }
}